This is my HealingMacro. I don't use the TidalForce with this one though but it does show the rest of it different from what you have that may make a difference. It also doesn't take into account the new @ values as I haven't touched my macros since 3.3 came out rofl. So been a while.
Code:
#showtooltip Healing Wave
/cast [target=mouseover,help,exists] [target=target,help,nodead] [target=targettarget,help,nodead] [target=player] Healing Wave
Hmm, looking at my Instant Heal Macro below I am now wondering if Tidal Force and/or Nature's Swiftness hit the global cooldown and thus cannot be used at the same time. Try without Tidal Force and then Nature's Swiftness and see if that points to both working together being the problem and not the macro itself.
Code:
#showtooltip
/cast Nature's Swiftness
/cast Healing Wave
Looking at your macro and mine it looks like yours should work fine unless it is working as I thought with a global cooldown hiccough.